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Header Override vs Kernline

A side-by-side comparison built from both listings. Blank cells mean the company has not given that detail; we never guess.

Header Override compared with Kernline
DetailHeader Override logo Header OverrideKernline logo Kernline
What it doesOpen-source browser extension to modify HTTP request and response headers and cookies Give your AI the exact component from any site, not a screenshot
StageNot given Not given
FoundedNot given Not given
Based inNot given ZA
Pricing modelOpen source Freemium
PricingNot given Free: $0 with 3 Copy for AI and 3 Component captures a day. Pro yearly: $36/year ($3/month). Pro monthly: $6/month. Lifetime Pro: $59 one-time payment.
Key features
  • Modify request and response headers with a focused editor interface
  • Scope rules to specific URLs using browser-supported filter patterns
  • Customize response cookies with Domain, Path, SameSite, Lifetime, Max-Age, and Secure attributes
  • Create up to five local rule profiles for different projects and test setups
  • Import and export profiles as local JSON files between browsers
  • Enable, disable, delete, and annotate rules with comments
  • Support for Chrome, Edge, and Firefox
  • All rules stored locally in browser with no server transmission
  • Component capture as HTML, React, or Vue with Tailwind
  • Tailwind v3 and v4 class export
  • Design token export as CSS variables or Tailwind theme
  • CSS inspector with box model and typography
  • Asset list for images, SVGs, icons, and fonts
  • Pixel-perfect mockup overlay with layers
  • Single-element or full-page Tailwind scanning
  • Offline inspection and copy functionality
What makes it different
  • Open-source with MIT License and full transparency
  • Rules stored entirely locally with no analytics, tracking, or external servers
  • Lightweight alternative to ModHeader
  • URL scoping prevents rules from affecting unintended websites
  • Simple interface requires no coding knowledge
  • Works entirely in your browser with no page uploads or tracking
  • Runs only on the tab you open and never uploads the page
  • No ads, tracking, or data selling
  • Copy real styles and tokens from live websites instead of screenshots
Free planNot given Not given
Open sourceNot given Not given
PlatformsNot given Not given
Public APINot given Not given
Community votes00
DR (Domain Rating by Ahrefs)15 +1 (up) since last checkNot checked yet no change since last check
Trust Flow (Majestic)30
Citation Flow (Majestic)180
Referring domains (Majestic)130

4 details filled in for both companies.

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